Synthetic plastic sleeve bearing having improved heat transfer characteristics

ABSTRACT

A sleeve bearing of synthetic plastic material wherein the inner and outer bearing surfaces are entirely of the plastic material. A heat conducting, reinforcing element, preferably a perforated metal sleeve, is fixed within the plastic bearing. In one embodiment, the metal sleeve is surrounded by the synthetic plastic material over its entire axial length and is exposed at one end to provide an axial heat transfering surface. In another embodiment, the sleeve is surrounded for a major portion of its length and exposed for a minor portion thereof to provide both radial and axial heat transferring surfaces.

United States Patent [191 Sievenpiper [54] SYNTHETIC PLASHC SLEEVE3,268,280 8/1966 Millet ..308/238 1; BEARING HAVING IMPROVEDHEAT3,347,737 10/1967 l-la rford ..308/238 x T A S R H QR QC R TI S3,397,856 8/1968 Sullivan et al.... ..308/238 FE C TE 8 C 3,400,9379/1968 Crankshaw ..308/238 [75 Inventor: Ward Sievenpiper, Alden, N.Y.[73] Assignee: Automatic Sprinkler Corporation of Primary ExamifwrAlalf.c,ohan 1 America, Cleveland, Ohio Asszstant Exqmm'er-IrWm C. CohenAttorney-Christel & Bean [22] Filed: Apr. 7, 1969 [21] Appl. No.:813,990 ABSTRACT 1 A sleeve of synthetic plastic material wherein 52 US.Cl. ..92/168, 92/53, 308/238, the hirer and Outer bearing surfaces are iy of the [511 1111.01. ..F16j 15/18, F166 27/02 plastic material A heatconducting, n ng [58] Field ofSearch...92/l68, 165,53, 170; 308/238 mm,preferably a perforated metal sleeve. is fixed within the plasticbearing. In one embodiment, the [56] References Cited metal slecve issurrounded by the synthetic plastic I material over its entire axiallength and is exposed at UNITED STATES PATENTS one end to provide anaxial heat transfering surface. In 2,622,949 12/1952 Cotchett ..308/238amher embwimem, 1 Sleeve is surmlinded for 2,639,198 5/1953 Kirkham..308/238 major Portion of its length and exposed for a minor 2,702,7302/ 1955 Ivanoff et 308/238 X portion thereof to provide both radial andaxial heat 2,888,879 6/1959 Gaarder ..92/170X 1 transferring surfaces. 13,072,449 1/1963 Morley et a1. ..308/238 3,136,221 6/1964 Walker ..92/53x 8 Claims, 5 Drawing Figures PATENTEUHARZIIBYS SHEET 10F 2 IN VENTOR.

WA/PD 5/5 VENP/PER A TTORNEYS PATENTEDHARZY I975 SHEET 2 OF 2 I N VENTOR.

WARD SIE VE/YP/PER ATTORNE Y5 SYNTHETIC PLASTIC SLEEVE BEARING HAVINGIMPROVED HEAT TRANSFER CHARACTERISTICS BACKGROUND OF THE INVENTION Thisinvention relates to sleeve bearings and, more particularly, tosynthetic plastic sleeve bearings having improved heat transfercharacteristics.

Sleeve-type bearings are widely used in various types of machines, oneexample being in a hydraulic cylinder, and in the past it has beenconventional to form such sleeve-type bearings of metal. Manydifficulties have been encountered with the use of metal bearings, suchas relatively poor wear life, need for periodic lubrication, andsusceptibility to corrosion.

More recently, sleeve bearings have been proposed and patented whichutilize a suitable synthetic plastic material, such as nylon or Teflon.Such synthetic plastics are desirably and advantageously resistant tophysical abrasion and corrosion and have natural lubricatingcharacteristics and low frictional coefficients. These synthetic plasticmaterials, however, have the disadvantage of being dimensionallyunstable under pressure and temperature both while being made and duringuse. More specifically, such materials tend to shrink as they coolfollowing the high temperature forming operation with the result thatthe cross section of a sleeve bearing becomes bowed inwardly. Thisresult is undesirable for most bearing applications and especially inhydraulic cylinders where it would allow leakage. The shrinkage isapparently due to the slowness with which the bearing cools after theforming operation.

' Such bearings have been found to experience serious dimensionalchanges due to the heat produced during use and sometimes even duringnormal changes in temperature and humidity conditions. The dimensionalchanges are apparently due to the slowness with which the bearingconducts heat.

' synthetic plastic material forms the bearing surface and One solutionwhich has been proposed is a metal reinforcing element entirely imbeddedwithin the synthetic plastic sleeve. This structure, however, servesonly to counteract the dimensional changes rather than to eliminate thecause of such changes and proves inadequate when relatively highoperating temperatures are encountered.

Another solution provides a metal reinforcing element surrounding andexposed on one, usually the outer, surface of the bearing. This type ofbearing obviously is limited to applications where only one bearingsurface is needed, if r the advantage of the synthetic plastic bearingsurface is to be utilized and would, for example, be undesirable in ahydraulic cylinder where both the inner and outer bearing surfaces mustbe used.

A third solution wherein a metal reinforcing element is partiallyimbedded in the synthetic plastic sleeve and partially exposed along onesurface thereof neverthe SUMMARY OF THE INVENTION It is, therefore, anobject of this invention to provide a sleeve bearing of syntheticplastic material which will not experience shrinkage and otherdimensional a heat conducting element is fixed therein. Both the innerand outer sleeve bearing surfaces are entirely and solely of syntheticplastic material. The heat conducting element is exposed in a manner soas to provide significant radial and/or axial heat transfer from aportion relatively small compared to the bearing surface but largecompared to the reinforcing member.

These and other advantages and characterizing features of the presentinvention will. become clearly apparent upon a reading of the foregoingdescription together with the included drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view,partially in section, of a hydraulic cylinder equipped with twoembodiments of the sleeve bearing provided by this invention;

FIG. 2 is an enlarged end view, partly in section, of one of the sleevebearings shown in. FIG. 1; I

FIG. 3 is a sectional view thereof taken about on line 3-3 in FIG. 2;

FIG. 4 is an enlarged end view, partly in section, of the other sleevebearing shown in FIG. 1; and

FIG. 5 is a sectional view thereof taken about on lines 5 -5 in FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED:

' EMBODIMENTS The sleeve bearing provided by this invention may be usedadvantageously in an hydraulic cylinder and thus for purposes ofillustration, is shown in FIG. 1 in conjunction therewith. The hydrauliccylinder itself comprises no part of the present invention, and itshould be noted that the sleeve bearing contemplated by this inventioncan be utilized in a wide variety of other applications.

Referring now to FIG. 1 there is shown a hydraulic cylinder 10 of thetelescopic type having a tubular casing 11 which is closed at one endthereof, the upper end in FIG. 1, by an end member 12 to which isattached a connecting member 13 which enables connection of this end ofthe cylinder 10 to the machine in which it is employed. The hydrauliccylinder, being of the telescopic type, includes a plurality ofconcentric tubes within the casing 11 which are adapted to bereciprocated relative to each other and to the casing. In thisparticular illustration there is shown an assembly of first, second andthird stage tubes 14, 15 and 16, respectively. At the upper end of theassembly there is provided a series of snap-fit retainer rings 17, 18, ase ries of piston rings 19, 20, 21 and a. series of guide rings 22, 23,24 for positioning and spacing the tubes in a conventional manner.

At the lower end of the hydraulic cylinder a cylinder rod 25 whichextends into the casing l 1 within the assembly of tubes 14-16terminates externally in a member 26 which enables connection of thisend of the cylinder 10 to the machine in which it is employed. The rod25, tubes 14-16 and casing 11 are thus disposed in a telescopingrelation to each other and the spaces between casing 11 and tube 14 andbetween the other tubes are closed at this end by a series of endmembers, often designated as cartridge nuts, shown at 27-29 in FIG. 1.The members 27-29 are positioned on the end of a corresponding tube orof the casing 11 and secured thereto by suitable means such as a setscrew, one of which is shown at 30. Each of the members 27-29 isprovided with a corresponding wiper member 31-33, respectively, aroundthe inner diameter thereof which contacts the particular tube which isreciprocable therethrough.

The cylinder 10 is provided at this end with the sleeve bearings of thepresent invention which are positioned between adjacent tubes and casingin the following manner.

One embodiment 40 of the sleeve bearing is located so that an endthereof is in contact with a corresponding one of the cartridge nuts27-29, the prime and double prime superscripts indicating that identicalbearings of progressively smaller diameters are included. Positionedadjacent the other end of each bearing 40 is a conventional packingmember, designated 41, 42 and 43. J

Positioned adjacent the packing members and above the bearing 40 in FIG.1 is a second embodiment 44 of the sleeve bearing contemplated by thisinvention, the prime and double prime superscripts again indicating thatidentical bearings of progressively smaller diameters are included. Eachbearing 44 is provided with a shoulder on the one end thereof, onepurpose of which is to support a corresponding one of a series of stoprings 45-47 each of which partially fits in a recess provided on theinner surface of the corresponding outer tube or casing.

As a result of this arrangement, the hydraulic cylinder 10 is affordedall the advantages provided by sleeve bearings having inner and outerbearing surfaces entirely of synthetic plastic material. Moreover, andwithout sacrificing any of these advantages, the bearings themselves areconstructed so as to have enhanced heat transfer characteristics whichprevent the cause of dimensional changes in the bearings which wouldotherwise occur when they are subjected to high operating temperatures.The manner in which these results are achieved will now be described.

FIGS. 2-5 show in more detail the two embodiments of the sleeve bearingconstructed in accordance with the present invention. One syntheticplastic material which can be utilized for forming the bearing is Nylon.Its low friction characteristics and resistance to chemical action andphysical abrasion are desirable for bearing usage. Another desirablesynthetic plastic material having similar characteristics is thetetrofluoroethylene fluorocarbon resin marketed under the trademarkTeflon."

One particular composition which was found to have highly advantageouscharacteristics as a bearing material consists, by weight, of 65-70percent nylon with filler material including 25-30 percent groundfiberglass and 5 percent molybdenum disulphide. Alternatively, Teflonmay be substituted for nylon in about the same proportion by weight. Thefiberglass filler enhances the strength of the bearing material so as toincrease its wear life, and the molybdenum disulphide enhances itlubricity.

The sleeve bearing of the present invention includes a reinforcingelement of good heat conducting material fixed therein. In preferredform the element is a metal strip, such as steel, which is perforatedover its entire surface and rolled to a sleeve of generally cylindricalshape. The diameter of the metal sleeve will, of course, vary inaccordance with the particular bearing diameter selected.

The sleeve bearing is then formed by first placing the perforatedreinforcing element in the die of a conventional injection moldingmachine. The synthetic plastic material is then injection molded in themetal sleeve in intimate contact with both the inner and outer surfacesthereof. During the molding operation the synthetic plastic material isextruded into the perforations of the metal sleeve. The portions of thematerial which project through the perforations form integralconnections between the material overlying one surface of the metalsleeve and the material on the other surface of the sleeve and thus bindthe whole together even though the synthetic plastic material maynormally have no significant adhesion for metal.

It is a particular feature of the present invention that the sleevebearing has a structure which enhances the heat transfer characteristicsthereof while not requiring any sacrifice in the advantages provided byan entirely plastic bearing surface. Referring now to FIGS. 2 and 3, thesleeve bearing designated 40 in FIG. 1 is shown in greater detail. Thesleeve of synthetic plastic material forms the inner and outer bearingsurfaces 50 and-51, respectively, and a perforated metal sleeve 52 isfixed therein. The reinforcing element or sleeve 52 is surrounded overit entire length by the synthetic plastic material. The inner and outerbearing surfaces 50 and 51 are thus entirely of the plastic material.The sleeve- 52 is exposed at one end 53 which is at the end of thesleeve bearing 40 but not on either of the bearing surfaces 50, 51. Thesleeve 52 thus conducts heat axially through the bearing and the exposedend 53 transfers the heat, for example, to the surface of the injectionmold after the bearing has been formed and is allowed to cool or to thesurface of an adjacent part or member when the bearing is in use in amachine. This arrangement provides axial heat transfer from an areawhich is relatively small compared to the bearing-surfaces butrelatively significant compared to the heat transfering member in thatit is the entire cross-sectional area thereof. As seen in FIG. 1, theexposed end 53 of sleeve 52 would be in contact with the associated nut27-29 for transfering heat thereto.

FIGS. 4 and 5 show the bearing designated 44 in FIG. 1 which, inaddition to transfering heat axially, also transfers heat radiallyoutwardly. The sleeve of synthetic plastic material forms the inner andouter bearing surfaces and 61, respectively, and a perforated metalsleeve 62 is fixed therein. The reinforcing element or sleeve 62 issurrounded for a major portion of its axial length by the syntheticplastic material. This separated by the surface 63. The shoulder sodefined by i the surfaces 63, 65 may be formed, for example, by removinga preselected amount of the plastic material and metal sleeve byconventional machining techniques. While the bearing in this particularillustration is constructed so that the surface 63 is exposed radiallyoutwardly, the bearing could be reversely con structed so that thesurface is exposed radially inwardly without departing from the spiritand scope of this invention.

Bearing 44 thus provides a significant amount of heat transfer by virtueof the radial and axial heat transfering surfaces. This structureprovides radialand axial heat transfer from a portion relatively smallcompared to the bearing surface but relatively large compared to thesleeve, in that the portion includes the whole crosssectional area plusa part of the radial surface. In addition, these heat transferingsurfaces define a shoulder which can support another part, for example astop ring, when metal-to-metal contact is desired as will be explainedpresently.

The sleeve bearings of the present invention, having improved heattransfer characteristics, were found to cool rapidly enough after thehigh temperature forming process so as to avoid the problem ofshrinkage. The heat conducting element, being exposed in a manneraccording to this invention, acts as a heat sink to hasten the coolingand setting of the plastic when the bearing cools after forming. This,in turn, prevents the bearing from bowing inwardly through thecross-section thereof. The same element when in contact with other heatconducting elements while the bearing is in use,

again acts as a heat sink to enhance the transfer of heat.

through the bearing so as to avoid the causes of dimensionalinstability.

As shown in FIG. 1, bearing 40 is disposed so that the heat transferingelement therein is in contact at the exposed end 53 thereof with thecylinder end member, such as cartridge nut 27. Heat is transferred in anaxial direction through the bearing to the end member, which is of heatconducting material, from which it is transferred further or dissapated.The bearing 44 is disposed so that the shoulder 63, 65 at the one endthereof abuts and firmly supports an adjacent member,

such as stop ring 45, 46 or 47. The shoulder is defined by the exposedheat transfering surfaces which are often and preferably of metal. Whenan adjacent metal member is to be supported firmly by the bearing,metalto-metal contact is frequently preferred to metal-toplasticcontact. Heat transfer is in an axial direction through bearing 44 tothe shoulder portion 63, 65 from which heat flows axially and radiallyand through adjacent member such as the stop ring 4547 and easing ortube. It should be noted that the advantages of enhanced heat transferand metal to-metal supporting contact are provided while still havinginner and outer bearing surfaces entirely of plastic material.

Accordingly, it is seen that the instant invention fully accomplishesits intended objects. While this invention hasbeemdescribed withspecificity, this has beenidone by way of illustration without thoughtof limitation.

I claim:

1. A sleeve type bearing comprising a synthetic plastic material formingthe bearing surface and an element fixed therein and formed of heatconducting material, said element having a major portion thereofembedded within said synthetic plastic material to provide inner andouter bearing surfaces entirely of said plastic material, said bearinghaving a shoulder formed at one end thereof exposing a minor portion ofsaid element in radial and axial directions relative to said bearing fortransferring heat in radial and axial directions.

2. The hearing as defined in claim 1 wherein said element is a hollowcylinder having one end thereof externally exposed at one end of saidsleeve.

3. The bearing as defined in claim 1 wherein said element is aperforated metal hollow cylinder.

4. The bearing as defined in claim 1 wherein said synthetic plasticmaterial consists, by weight, of about 6570 percent resin such as Teflonor nylon, about 25-30 percent ground fiberglass and about 5 percentmolybdenum disulphide.

5. The bearing as defined in claim 2 wherein a portion of said syntheticplastic material and of said cylinder is removed at one end to providesaid shoulder having a radial heat transferring surface and two axialheat transferring surfaces separated by said radial surface.

6. In a hydraulic cylinder including a first cylinder reciprocablewithin a second cylinder spaced radially therefrom and wherein anannular closure member is secured to one end of said second cylinder andis provided with an opening sufficient to allow passage of said firstcylinder therethrough, the improvement comprising:

a. a first sleeve type bearing of synthetic plastic material having aninner bearing surface contacting said first cylinder and an outerbearing contacting said second cylinder, said bearing also having a heattransferring element having a major portion thereof embedded-within saidinner and outer surfaces and exposed at one end thereof in radial andaxial directions in a manner defining a shoulder at one end of saidbearing; and

b. means abutting said bearing at each end thereof for preventing axialmovement thereof.

7. In a hydraulic cylinder as defined in claim 6, said means abutingsaid bearing comprises an annular member supported by said shoulder andheld in fixed axial relation to said cylinders and a packing member atthe other end of said bearing.

8. In a hydraulic cylinder as defined in claim 6, the improvementfurther comprising:

a. a second sleeve type bearing of synthetic plastic material having aninner bearing surface contact ing said first cylinder and an outerbearing surface contacting said second cylinder, said bearing alsohaving a heat transfering element having a major portion thereofembedded within said inner and outer surfaces and exposed at one endthereof in an axial direction; and

b. said second bearing located so as to be spaced from said firstbearing and being disposed so hat said heat transfering element is inaxial contact with said annular closure member.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,722,375 Dated March 27, 1973 Inventor(s) Ward Sievenpiper It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In item [73] of the heading, the name of the Assignee should be A-T-OInc.

Signed and sealed this 30th day of April 197R.

(SEAL) Attest:

IBDJJARD I-LFLETCHERJR. I 0 MARSHALL DAMN Attesting Gfficer Commissionerof Patents FORM P0405, (w'sg) USCOMM-DC scan-Pee

1. A sleeve type bearing comprising a synthetic plastic material formingthe bearing surface and an element fixed therein and formed of heatconducting material, said element having a major portion thereofembedded within said synthetic plastic material to provide inner andouter bearing surfaces entirely of said plastic material, said bearinghaving a shoulder formed at one end thereof exposing a minor portion ofsaid element in radial and axial directions relative to said bearing fortransferring heat in radial and axial directions.
 2. The bearing asdefined in claim 1 wherein said element is a hollow cylinder having oneend thereof externally exposed at one end of said sleeve.
 3. The bearingas defined in claim 1 wherein said element is a perforated metal hollowcylinder.
 4. The bearing as defined in claim 1 wherein said syntheticplastic material consists, by weight, of about 65-70 percent resin suchas Teflon or nylon, about 25-30 percent ground fiberglass and about 5percent molybdenum disulphide.
 5. The bearing as defined in claim 2wherein a portion of said synthetic plastic material and of saidcylinder is removed at one end to provide said shoulder having a radialheat transferring surface and two axial heat transferring surfacesseparated by said radial surface.
 6. In a hydraulic cylinder including afirst cylinder reciprocable within a second cylinder spaced radiallytherefrom and wherein an annular closure member is secured to one end ofsaid second cylinder and is provided with an opening sufficient to allowpassage of said first cylinder therethrough, the improvement comprising:a. a first sleeve type bearing of synthetic plastic material having aninner bearing surface contacting said first cylinder and an outerbearing contacting said second cylinder, said bearing also having a heattransferring element having a major portion thereof embedded withIn saidinner and outer surfaces and exposed at one end thereof in radial andaxial directions in a manner defining a shoulder at one end of saidbearing; and b. means abutting said bearing at each end thereof forpreventing axial movement thereof.
 7. In a hydraulic cylinder as definedin claim 6, said means abuting said bearing comprises an annular membersupported by said shoulder and held in fixed axial relation to saidcylinders and a packing member at the other end of said bearing.
 8. In ahydraulic cylinder as defined in claim 6, the improvement furthercomprising: a. a second sleeve type bearing of synthetic plasticmaterial having an inner bearing surface contacting said first cylinderand an outer bearing surface contacting said second cylinder, saidbearing also having a heat transfering element having a major portionthereof embedded within said inner and outer surfaces and exposed at oneend thereof in an axial direction; and b. said second bearing located soas to be spaced from said first bearing and being disposed so that saidheat transfering element is in axial contact with said annular closuremember.